Synchronizing WiMAX Synthesizer TRF1x21/TRF1x12 to Arbitrary Reference

Texas Instruments has a WIMAX RF chipset for base station and CPE applications that include integrated synthesizers to realize the superheterodyne architecture. For optimum channel resolution, these devices must be tied to an 18-MHz reference frequency. In some systems, the synthesizer reference frequency needs to be synchronized to a system reference frequency that may not be an integral multiple of 18 MHz. This application report presents the circuitry required to synchronize the 18-MHz reference to an arbitrary system reference clock and illustrates that negligible degradation occurs in the RF performance of the radio.